This invention relates to a system for recovering the vapor displaced from a fuel tank during fuel fill using valve apparatus for control of vapor flow to a storage canister and recirculation of a portion of the vapor via the fill pipe.
Emission control standards for vehicle fuel systems are now beginning to require recovery of fuel vapors displaced from a vehicle fuel tank during refueling. U.S. Pat. No. 4,762,156 to Rich discusses the use of a liquid seal in a fuel fill pipe with a vapor recirculation system to replace air which would otherwise be drawn into the fill pipe and entrained by the inrushing fuel. Such entrained air has been shown to increase the generation of vapor within the tank during refueling through liquid seals; and the additional vapor would necessitate a larger storage canister. The Rich apparatus uses a vapor vent valve actuated during refueling to allow a flow of displaced vapor to a storage canister and a separate recirculation valve apparatus effective to recirculate a portion of the displaced vapor to the fuel fill pipe at the filler neck for entrainment in the inrushing fuel at a rate depending on the rate of fuel flow. The vapor so entrained reduces the air drawn into the fill pipe by the inrushing fuel; and this reduces the tendency for additional vapor to form in the process.